Add functional, but slow solution to E618.
Add functional, but slow solution to E618.

Based on
https://github.com/shlomif/project-euler/tree/master/project-euler/618 .

shlomif/perl6-examples,shlomif/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,perl6/perl6-examples,perl6/perl6-examples